Understand something about the $189 million luxury-tax threshold for next season. It isn’t really $189 million.

Each team is charged roughly $11 million for items such as insurance and pension. Thus, if the Yankees are going to get under — and I believe they are determined to do so — then they can pay their players about $178 million.

But wait. It isn’t like they could just get to $177.9 million in the offseason. They need to create spare money for promotions, potential bonuses reached and obtaining players via trade. Let’s make that a conservative $8 million.

OK, now we are talking about the Yanks having approximately $170 million for players next season. Assuming Derek Jeter picks up his option and Alex Rodriguez’s suspension is upheld, the Yanks would have six players signed for next season — Jeter, CC Sabathia, Mark Teixeira, Alfonso Soriano, Ichiro Suzuki and Vernon Wells. For luxury-tax purposes, that crew costs roughly $68.5 million.

That would leave a little more than $100 million to spend, and you can subtract about another $14million-$16 million to reach agreement with the arbitration-eligible Brett Gardner, David Robertson, Ivan Nova, Shawn Kelley and Francisco Cervelli. We can assume another $3-$4 million for five or six non-arbitration players such as David Phelps and Adam Warren.

That will leave around $80 million, and a good deal of that will be earmarked for Robinson Cano, Curtis Granderson, Hiroki Kuroda — or their replacements.

You can see how quickly the money goes and why the Yanks are pretty much desperate for A-Rod’s suspension to be upheld and his $27.5 million to go away from their ledger.

It means the Yanks are going to have to count pennies elsewhere in trying to still have a deep/contending roster with the $189 million constraints. Which puts them in an interesting decision-making place with five players currently on the roster:

BRENDAN RYAN — He’s a free agent who probably will cost $2-$3 million. He has shown his stellar defensive reputation is well earned and in a small sample has hit better than expected. With Jeter so uncertain, the Yanks need shortstop insurance. In addition, the Yanks might have to make the tough decision to defend for Jeter late in close games they are winning — and Ryan would be ideal for that.

EDUARDO NUNEZ — It is easy to want to give up on him. His game remains full of rough edges. His defense is better, but still not good. His offense offers promise, but never quite delivers. But Nunez is just 26. He has bat speed and athleticism mostly missing from the Yankees roster. He has hit .281 in 196 at-bats since returning from his second disabled-list stint. This might be all Nunez has, and the Yanks could decide to go with the steadier Jayson Nix, who is well liked by their decision-makers and would earn about $1.5 million through arbitration. But Nix does not have upside potential. The not-yet-arbitration-eligible Nunez does. However, he also has a minor league option, so maybe the Yanks re-sign Nix and stash Nunez at Triple-A.

MARK REYNOLDS — He is who we thought he was — low average, high strikeouts, monster power. If A-Rod does not come back, the Yanks are going to need either a singular or platoon response at third. Reynolds also offers some first base protection for Teixeira. He likely will cost $4 -$6 million. You could imagine the Yanks believing that could be spent better elsewhere.

AUSTIN ROMINE — Catching projects as a money-saving area for the Yanks. Chris Stewart, arbitration eligible, probably will not be asked back. I can see the Yanks going with Cervelli and Romine in the majors, stashing J.R. Murphy (who they like a lot) at Triple-A and hoping touted prospect Gary Sanchez makes big strides beginning at Double-A. Romine, like Nunez, got better as the season progressed (.773 OPS in his final 28 games). He is 24. Again, at some point, the Yanks are going to have to trust that some of their youth has ceilings still to reach.

MICHAEL PINEDA — Because he has accrued service time while on the DL, Pineda actually is arbitration eligible. But because he has not pitched in two years, he still will make just above the minimum. But the Yanks have maximum need for him.

Let’s assume Kuroda returns. That gives the Yanks a front three of Kuroda, Sabathia and Nova. They have Phelps, Warren, David Huff, Vidal Nuno and Brett Marshall to battle for a cheap No. 5. The value of having an inexpensive No. 4 with potential to be more could keep them from having to spend limited funds on a veteran starter. But can they trust Pineda? My gut says just to have other options they allocate $5 million and gamble on someone such as Mike Pelfrey or maybe even Roy Halladay, who didn’t throw harder than 83 mph in his last start.